Very young children who are late in reaching early language milestones (production of first words, growth of vocabulary, and combining words) may be at risk for later language impairment and/or learning disability. Because standardized tests and clinically reliable measures for determining which children will develop normally and which will remain delayed are not yet available, they are also at risk for being missed by pediatricians and other professionals on whom parents rely to make appropriate referrals. The major purpose of this project is to identify factors in children 18- to 24-months old which predict potential later language and learning deficits. This, in turn, will allow appropriate early identification and referral. The studies are designed to identify the nature of the relationships between language and nonverbal cognition in late talking toddlers, and to follow their development in those domains over 4 years. Late talkers will be compared to normal children of the same age, normal children at the same level of language development, and linguistically precocious children at each test time. The 3 control groups are followed longitudinally as well. For all control groups, development in linguistic and nonlinguistic domains will be measured and examined for associations and dissociations within and across domains (using ANOVA and DISCRIMINANT ANALYSIS). Specific domains being studied are language comprehension and production, use of symbolic gestures, spatial cognition, concept formation, and categorization. These domains will be analyzed to provide profiles of language and other cognitive variables which will serve as markers for those who are or are not likely to catch up linguistically. Since data will also be gathered longitudinally, information about the course of development will be obtained, giving information about the processes involved in catching up or falling behind. Longitudinal data will also provide information that will be used to design research on early assessment and intervention. Students will have individual projects, but will also learn by interacting with others in the lab and in group lab meetings. Each will meet regularly directly with the PI.